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Globally, many estuarine areas are suffering from large-scale land reclamations to fulfill the land demands of city expansion. Understanding the wave and storm surge evolutions in response to human reclamations in estuaries is of vital importance regarding estuarine management (e.g., reclamation plan formulation, flood mitigation). The wave and storm characteristics, and their responses to 1990–2020 land reclamations in the Pearl River Estuary (PRE) were investigated by a storm surge model. Besides, the impacts of increasing typhoon intensity (TI) on the changes of waves and storm surges caused by reclamations were also illustrated under the background of global warming. Simulated results show that reclamations cause apparent variations of wave height and storm surge fields in the PRE. The wave height and surge height also increase with the enhancement of TI, consequently influencing the wave height and surge height change rates caused by reclamations. Furthermore, the combined actions of land reclamation and increased TI conduct the most remarkable effects and bring the highest surge height compared with other scenarios. Particularly, the maximum wave height and surge height can reach 0.88–2.31 m and 2.71–3.77 m along the seawalls of Zhuhai, respectively, indicating more enormous seawall submersion and inland flooding. [Display omitted] • Land reclamations cause apparent variation of wave and storm surge fields. • Wave height and surge height present higher values for larger typhoon intensity, thus changing reclamation impacts. • The combination of land reclamation and increased typhoon intensity causes more enormous inland flooding. [ABSTRACT FROM AUTHOR]

The time required for water renewal in an estuary is closely related to its self-purification ability and environment degree. A FVCOM-based water age (WA) model was conducted to investigate the renewal timescale in the Pearl River Estuary (PRE) under various hydrodynamic scenarios. Model sensitivities revealed the depth-averaged WA during the summer was significantly smaller than that during the winter; meanwhile, the region with vertically significant variations in the WA varied from almost the whole estuary to the downstream. It can be explained that the seaward residual currents became stronger and narrowed the region of vertical circulations by impeding salinity invasion and stratification. During typhoon Hagupit, the depth-averaged WA was apparently increased in the most of the estuary because the horizontal water circulations between the estuary and open sea were significantly decreased by the strong up-estuary surge-waves. Moreover, the vertical WA distribution almost became a single-layer structure with the severely weakened vertical circulations. After reclamations, the variable shorelines in the PRE significantly affected the hydrodynamic characteristics and water circulations, thus the depth-averaged WA complicatedly changed, and the vertical difference of the WA values slightly increased in narrowed waterways and their downstream due to the limited effects on the vertical circulations. • A 3D water age (WA) model is built to quantify water renewal in the Pearl River Estuary (PRE). • The WA in the PRE was characterized by significantly spatial distributions and seasonal variations. • The WA was significantly increased in the most areas and less stratified in vertical direction during typhoon Hagupit. • After reclamations, the WA complicatedly changed in horizontal direction and became more stratified in vertical direction. [ABSTRACT FROM AUTHOR]